Sorry if this question was asked before. (I looked but couldn’t find anything)

I maybe would like to buy some 40 round mags for competition.

So what mags are any good and what kind of upgrade do they need?

Like Magpul followers and springs.

Check the mag brand rating post at the top of the page.

I know of six kinds or brands. Western Metal, PMI, USA, Triple K, Sterling, And the new ones out National I think they are called.
The only kind I have are the PMI ones and they work for me with no problems The difference I noticed in them is the area below the mag catch is flat. No bump out like most mags have. Mine have worked for me 100% so far.

PMI's and Sterlings are the only ones you want to get, everything else is junk